For the first time the polynuclear hydroxido-bridged platinum(IV) nitrato complexes with nuclearity higher than two were isolated from nitric acid solutions of [Pt(H2O)(2)(OH)(4)] and crystallized as supramolecular Compounds of macrocyclic cavitands cucurbit[n]uril (CB[n], n 6,8) and 18-crown-6 ether: [Pt-4(mu(3)-OH)(2) (mu(2)-OH)(4)(NO3)(10)]center dot CB[6]center dot 25H(2)O (I), [Pt-6(mu(3)-OH)(4) (mu(2)-OH)(6)(NO3)(12)]-(NO3)(2)center dot CB[8]center dot 50H(2)O (II), and [H3O subset of 18-crown-6](2) [Pt-2(mu(2)-OH)(2)(NO3)(8)] [Pt-4(mu(3)-OH)(2)(mu(2)-OH)(4)(NO3)(10)] (III). The isolation of the compounds in the single crystalline state allows the determination of the structure of the tetranuclear and hexanuclear complexes [Pt-4(mu(3)-OH)(2)(mu(2)-OH)(4)(NO3)(10)] and [Pt-6(mu(3)-OH)(4)(mu(2)-OH)(6)(NO3)(12)](2+), which have been previously unknown, in the slid state. Stability of Pt-x(OH)(y) cores of the polynuclear nitrato complexes toward alkaline hydrolysis was verified by Pt-195 NMR spectroscopy. Analysis Of Pt-195 NMR spectra of the compound III reveals that addition of every Pt(mu-OH)(2)Pt ring results in, similar to 260 ppm downfield shift relative to the mononuclear form, which allows the prediction of signal positions for complexes of higher nuclearity.